Hi,

I assume that the tenant above is a private leaseholder (i.e. they own their flat under a long lease) and that your mother is a L&Q tenant?

If so, L&Q will likely be acting for agents for the freeholder (i.e. landlord) or in fact have had the freehold transferred to them by Lewisham Council in their management role.

It would be interesting to have a few more details as L&Q have a complaints procedure that can be commenced on-line or over the telephone and this usually resolves such issues. If L&Q are the landlord then they should be enforcing the alleged breach by the tenant above if the water ingress is from their flat.